The present invention relates to fabrication of dielectric and conductive features. In some embodiments, the conductive features provide decoupling capacitors or ground planes for interposers for integrated circuits. The present invention also relates to chemical mechanical polishing (CMP).
Decoupling capacitors can be connected between the power and ground terminals of an integrated circuit to filter out power supply noise or provide a charge reservoir for power consumption variations. The decoupling capacitor should be placed as close as possible to the integrated circuit's power and ground inputs in order to reduce the parasitic inductance. To meet this placement objective, the capacitor can be manufactured in an interposer 110 (FIG. 1) soldered between the integrated circuit 120 and a ceramic chip carrier 124. In this example, the interposer is itself an integrated circuit, manufactured on a silicon wafer 128. Silicon oxide 132 is formed on wafer 128. Conductive layer 136, dielectric 140, and another conductive layer 144 are formed on oxide 132. Layers 136, 140, 144 are patterned to provide a decoupling capacitor 150. Additional dielectric 156 is deposited over the structure. Vias 164, 168 are formed in dielectric 156 to allow contact to the respective capacitor plates 136, 144. Vias 164, 168 are filled with metal. Vias 174, 178 are made through the interposer and filled with metal. These vias are electrically connected to the metallized vias 164, 168. Vias 174, 178 receive respective power and ground signals from chip carrier 124 and provide these signals to IC 120. Additional metallized vias 182 pass through the interposer and provide signal paths between chip carrier 124 and IC 120. The interposer is soldered to IC 120 and ceramic substrate 124 with solder balls 186. See U.S. Pat. No. 6,943,108 B2 issued Sep. 13, 2005 to Farooq et al. and incorporated herein by reference.
Alternative fabrication techniques and structures are desirable for decoupling capacitors and other conductive and dielectric features of interposers and other structures.